I'd strongly suggest restarting. As you have already noticed, if you don't specialize, your character will be too weak to handle the enemies. If you want a pistoleer with explosions and psi, then I'd recommend guns and grenades (for explosions), with help from temporal & psychokinesis psi (which have abilities that work even with 3 will).
edit: I've misunderstood. If all you want is guns and explosion and mind powers, look up smgs builds and add psi to the mix.
For psi, it's the invested number that counts for learning psi abilities, not the effective skill, so don't worry your 3 will lowers it a bit. Once you get temporal psi to 25 and psychokinesis to 25, take the psi pill. Buy limited temporal increment from Ethan (he will actually give one ability to you for free if you play a gal). This works very well together with the grenadier feat. Throw one molotv/frag grenade in the first turn > limited temporal increment, and you can throw another in the next turn. Buy force field from Bison, and once you get psychokinesis to 30, buy electrokinesis. While the electrical damage will be low, you want electrokinesis for the very useful stun.
